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yap-6.3/library/arg.yap
Vítor Santos Costa 15404b3835 small
- do not call goal expansion on meta-calls (that is done by undef).
- docs updates
- fix init code
2015-12-15 09:28:43 +00:00

166 lines
3.3 KiB
Prolog

/**
* @file arg.yap
* @author VITOR SANTOS COSTA <vsc@VITORs-MBP.lan>
* @date Tue Nov 17 01:08:55 2015
*
* @brief arg/3 and friends
*/
:- module(arg,
[
genarg/3,
arg0/3,
genarg0/3,
args/3,
args0/3,
% project/3
path_arg/3
]).
/**
* @defgroup arg Term Argument Manipulation.
@ingroup @library
@{
Extends arg/3 by including backtracking through arguments and access
to sub-arguments,
- arg0/3
- args/3
- args0/3
- genarg/3
- genarg0/3
- path_arg/3
It is based on the Quintus Prolog arg library. Except for project, all
predicates use the arg/3 argument pattern.
This file has been included in the YAP library by Vitor Santos Costa, 2008. No error checking is actuallly performed within the package: this left to the C-code thaat implements arg/3 and
genarg/3.
*/
/**
* @pred arg0( +_Index_, +_Term_ , -_Arg_ )
*
* Similar to arg/3, but `arg0(0,_T_,_F_)` unifies _F_ with _T_'s principal functor:
~~~~~~~~~
?- arg0(0, f(a,b), A).
A = f.
?- arg0(1, f(a,b), A).
A = a.
?- arg0(2, f(a,b), A).
A = b.
~~~~~~~~~
*/
arg0(0,T,A) :- !,
functor(T,A,_).
arg0(I,T,A) :-
arg(I,T,A).
/**
* @pred genarg0( +_Index_, +_Term_ , -_Arg_ )
*
* Similar to genarg/3, but `genarg0(0,_T_,_F_)` unifies _F_ with _T_'s principal functor:
~~~~~~~~~
?- genarg0(I,f(a,b),A).
A = f,
I = 0 ? ;
A = a,
I = 1 ? ;
A = b,
I = 2.
~~~~~~~~~
*/
genarg0(I,T,A) :-
nonvar(I), !,
arg0(I,T,A).
genarg0(0,T,A) :-
functor(T,A,_).
genarg0(I,T,A) :-
genarg(I,T,A).
/**
* @pred args( +_Index_, +_ListOfTerms_ , -_ListOfArgs_ )
*
* Succeeds if _ListOfArgs_ unifies with the application of genarg/3 to every element of _ListOfTerms_.
It corresponds to calling maplist/3 on genarg/3:
~~~~~~~~~
args( I, Ts, As) :-
maplist( genarg(I), Ts, As).
~~~~~~~~~
Notice that unification allows _ListOfArgs_ to be bound, eg:
~~~~~~~~~
?- args(1, [X1+Y1,X2-Y2,X3*Y3,X4/Y4], [1,1,1,1]).
X1 = X2 = X3 = X4 = 1.
~~~~~~~~~
*/
args(_,[],[]).
args(I,[T|List],[A|ArgList]) :-
genarg(I, T, A),
args(I, List, ArgList).
/**
* @pred args0( +_Index_, +_ListOfTerms_ , -_ListOfArgs_ )
*
* Succeeds if _ListOfArgs_ unifies with the application of genarg0/3 to every element of _ListOfTerms_.
It corresponds to calling maplist/3 on genarg0/3:
~~~~~~~~~
args( I, Ts, As) :-
maplist( genarg0(I), Ts, As).
~~~~~~~~~
Notice that unification allows _ListOfArgs_ to be bound, eg:
~~~~~~~~~
?- args(1, [X1+Y1,X2-Y2,X3*Y3,X4/Y4], [1,1,1,1]).
X1 = X2 = X3 = X4 = 1.
~~~~~~~~~
*/
args0(_,[],[]).
args0(I,[T|List],[A|ArgList]) :-
genarg(I, T, A),
args0(I, List, ArgList).
/**
* @pred args0( +_ListOfTerms_ , +_Index_, -_ListOfArgs_ )
*
* Succeeds if _ListOfArgs_ unifies with the application of genarg0/3 to every element of _ListOfTerms_.
It corresponds to calling args0/3 but with a different order.
*/
project(Terms, Index, Args) :-
args0(Index, Terms, Args).
% no error checking here!
/**
* @pred path_arg( +_Path_ , +_Term_, -_Arg_ )
*
* Succeeds if _Path_ is empty and _Arg unifies with _Term_, or if _Path_ is a list with _Head_ and _Tail_, genarg/3 succeeds on the current term, and path_arg/3 succeeds on its argument.
*
* Notice that it can be used to enumerate all possible paths in a term.
*/
path_arg([], Term, Term).
path_arg([Index|Indices], Term, SubTerm) :-
genarg(Index, Term, Arg),
path_arg(Indices, Arg, SubTerm).
%%@}